Allow pressing ACTION to skip fake loading screen

While there already exists an option to skip the fake loading screen
entirely (without requiring an ACTION press), there are several reasons
for including this option as well:

 * So people upgrading from 2.2 won't have to sit through the fake
   loading screen the first time they open 2.3.

 * So if people are too lazy to use the existing option, they can use
   this one instead.

 * So tool-assisted speedruns (TASes) of this game can skip the fake
   loading screen without requiring an existing settings.vvv beforehand.

   This last one is the biggest reason for me, since I'm not sure what
   TASVideos.org rules are regarding existing save files, but with this
   change nobody has to worry about their rules and can safely just
   press ACTION to skip the fake loading screen automatically.

desktop_version/src/main.cpp

@@ -527,6 +527,7 @@ void inline fixedloop()
         switch(game.gamestate)
         {
         case PRELOADER:
+            preloaderinput();
             preloaderrenderfixed();
             break;
 #if !defined(NO_CUSTOM_LEVELS) && !defined(NO_EDITOR)

desktop_version/src/preloader.cpp

@@ -1,6 +1,7 @@
 #include "Enums.h"
 #include "Game.h"
 #include "Graphics.h"
+#include "KeyPoll.h"
 #include "UtilityClass.h"
 
 int pre_fakepercent=0, pre_transition=30;
@@ -10,6 +11,21 @@ int pre_darkcol=0, pre_lightcol=0, pre_curcol=0, pre_coltimer=0, pre_offset=0;
 int pre_frontrectx=30, pre_frontrecty=20, pre_frontrectw=260, pre_frontrecth=200;
 int pre_temprectx=0, pre_temprecty=0, pre_temprectw=320, pre_temprecth=240;
 
+void preloaderinput()
+{
+  game.press_action = false;
+
+  if (key.isDown(KEYBOARD_z) || key.isDown(KEYBOARD_SPACE) || key.isDown(KEYBOARD_v) || key.isDown(game.controllerButton_flip)) {
+    game.press_action = true;
+  }
+
+  if (game.press_action) {
+    //Skip to TITLEMODE immediately
+    game.gamestate = TITLEMODE;
+    game.jumpheld = true;
+  }
+}
+
 void preloaderrenderfixed()
 {
   if (pre_transition < 30) pre_transition--;

desktop_version/src/preloader.h

@@ -1,6 +1,8 @@
 #ifndef PRELOADER_H
 #define PRELOADER_H
 
+void preloaderinput();
+
 void preloaderrender();
 
 void preloaderrenderfixed();